Method of curing plastic articles



April 16, 1935. H. c. LORD METHOD OF CURING PLASTIC ARTICLES Original Filed Sept. 22

.Illllll 4 www@ Patented Apr. 16, 1935V UNITED STATE;

METHOD oF CURINGPLASTIG ARTICLES Y V Hugh C. Lord, Erie, Pa.'

Application September 22, 1930, Serial No. 483,461

Renewed September 14, 1934 1l Claims.

The particular exemplication of the invention is intended to cure rubberand in its preferred embodiment is arranged to cure rubber forming a wall between a central pin and an outer shell.

fx Heretofore such articles have been ordinarily cured by placing them in a mold with the shell in contact with the wall of the mold and exerting pressure 4on the ends of ther rubber. Usually this has been accomplished with a numberof such molds arranged sidev by sidejwithfa single source of pressure closing each of the -spaces. Such structures and methods of vulcaniz'ing, these articles are subject to serious objections, vas--with pmost articles of this kind -itis desirable tosubject the rubber adjacent'to the center'to at leastas great temperature as the-rubber toward'the shell and where the shell is brought into immediate contact with Vthe vwall of the mold it hasNa higher temperature than at the pin 'so that unless compensation is provided Aby compounding, which is oftendifcult, the rubbervis softerA at,V the pin than at-the shell Vwhich is just the kreverse lof what, underr ordinary conditions, should exist f because the massof rubber at the pin isvmuch less than that atvthe shell.

Further Where a number of articles are vulcanizedA together, side byvside, itis very difcult to get them all within suchclose tolerances that the closure on all of them isuniform. i For vthis reason it has been common to bottom the -mold on the central pin which is usually better vcapable'of lsustaining the 1 pressure-than the shell. yThis haspermitted 'the'over-llow of rubber to Vthe space between .the shell and thevmold, thus making itV diicult to; remove thearticles from ,themold and also to maintain a-proper molding pressure -on the: rubber during; vulcanization. With the present invention, the articles are arranged so as to receive their vdirectvheat for vulcanization from'the ends, the shells being spaced from the heat-exchanging walls; Y inasmuch as the central pin is usually of an area'more Vreadily conveying .heat the temperature atA the pin maybe maintained'equal to that at the shell. This spacing the shell from the-walls also pro- Vides a space for an over-now of rubber which ,obviates the nice proportioning, or weighing of the rubber for the space, andathusjsimpliiies fabrication. 1?- i 'f v1 o In the present invention,- in the preferred form, caps are provided which'engage'the' ends of the articles and these caps are arranged` in a series guided preferably by a: steam-heated tube vso that when pressure is-.eXerted on vthe end of 'v the series 'all' of thev series'receive the'same pressure regardless of small diierences in the lengths of the articles. `This makes it possible to permitof very much larger tolerances and simplifies the fabrication. It also makes it possible to assure-the amount of pressure with which the rubber is sealed lin the space within the shell, and thusit vis possible to proportion the pressure to the capacity offthe shell to sustain it.A lt also makes it possible to so arrange the pin and shell t that the bottoming of the .caps will2 be on the shell so that there is a direct sealing closure of the cap on the `shell with a permissible over-dow Ato the point of closure. Without such a regulated pressure as ispossible with a single source of pressure on the series in tandem there would be more or less upsetting ofthe shell and with such upsettingof course, amis-sizing of the shell rand if there `were a'close tinthe mold great diiculty in removing the'articles.

The invention also involves aconvement means of loading and discharging the molds. Features and details of the invention will appear more fully from the speciiication and claims.

Avpreferredembodiment of the invention and the rnanneroi practicing the process is illustrated in the accompanying drawing as follows:-

. Fig. 1 shows a central section through the apparatus. Y Y l Fig. 2 an end view of theapparatus.

Fig. -3 an enlarged view of one ofthe curing tubes. Y f I Fig. 4 an -end view of the stop.

Fig. 5 an end -view of the socket receiving the lstop.-l

Fig.. 6 an end view of the loading tube.

I marks the tubular cases formingV the steam chamber. These are provided with heads 2. The cases'are arranged between uprights 3 and llythe headsvengaging the uprights. The cases are supported in a convenient manner in slightly spaced relation between the posts. The posts are connected` by cross pieces 5. are arranged vwithin the cases. They extend from head to head and form a closure with the head so asto form an annular steam space within the case. They are secured by nuts 6a. Caps 'l are arranged along the tube, end to end. These caps have taperedl sockets 8, the bottoms of which engage the endsof shells 9 and the periphery at the bottom centers the shell. The caps are` also provided with central sockets l0 which are adapted rto receive the vends ofthe center pinsA ll. These sockets locate the pins within` tolerances endwise and also lcenter the pins.

Preferably the,relation between the ends of the Gruidev tubes 6 and the tapered sockets is such that the bottoming pressure is received by the ends of the shells. A space I2 is provided around the shells and between the shells and the heated guide tube 6, and the over-flow I2@ of rubber runs into this space and is vulcanized Without pressure and may be readily detached. Pressure blocks I3, preferably air insulated, are arranged at the ends of the series. Ram cylinders I4 have their rear ends closed by heads I5. They are arranged between posts I6 and I'I and have their axes coincident with the tubes 6. The posts are connected by cross posts I8 and the thrust is sustained by a strain rod I9 connecting the'posts s and n. ders. These pass through` stuiling boxes 2| and are provided with ends 22 which, when the plungers are advanced extend into the tube Bland exert pressure on the end block I3 and consequently on `the series of caps and joints. Fluid pressure is communicated through pipe 23 which is connected with a supply pipe 2II, the pipes 23 being controlled by valves 25.V Pulleys 26 are arranged on the plungers 20 and stationary pulleys 26a are arranged at-each side of and adjacent to the cylinders. Cords 2Gb` are woven back and forth between these rpulleys and carried around guide pulleys 21 and 28 and secured to a weight 29. The purpose of this weightedcord is to retract the plungers. Y

A stop socket 30 is arranged at the rear end of each of the tubes opposite the plungers. These have inward projections 3I and a stop plug 32 having grooves 33 which permit them to be passed by the projections 3| and turned in the manner of a bayonet joint by means of a handle 34 so as to form a stop back of the end of the series of joints. Preferably the insulated plug I3 at this end of the mold is directly attached to the stop.

In order to conveniently load the guide tubes the joints are'placed in a loading tube 35. This tube has an end 36 which is adapted to close on a seat 37 in the bottom of the socket 30. It has grooves 39 which may be locked on the projections 3I so as to Vmaintain the loading tube in sealed connection with the guide tube. The opposite end of the loading tube has a head 38 which is provided with a socket 40 with inwardly extending pins 4I adapted to enter the grooves 39 of a head 36 at that end of the tube. A fluid supply, preferably air, is provided through `a. pipe 42 connected with the head 38. In order to empty the guide tube in which the vulcanization is completed a filled loading tube is connected, air supplied at the end of-the loading tube and this driving forward discharges the vulcanized articles. At the completion of the movement of the incoming tubes the air is shut off and the loading tube removed, the stop plug inserted, the plunger-again advanced and the vulcanizing operation started.

At the completion of the operation the plunger is retracted and the joints retarded'in the manner specified. Steam is delivered tothe cases through the pipe 43 from which the branch pipes 44 extend. Drainage is taken care of through a pipe 45 to which the branch pipes extend from each case.

' With this structure a very simple apparatus may be provided giving a very large capacity in a comparatively small space and in a very inexpensive manner. The water consumption on the plungers is very much reduced over. the molds Plungers are arranged in the cylin- 1,997,908' pins and their sockets and the ends of the shells` arranged in parallel in that a single column of water having the cross area of the plunger is used for a great many joints, whereas a similar amount of water would be used in the parallel system for each joint.

What I claim as new isz- '1. The method of curing plastic articles having outer shells, centering pins, and an intervening wall of plastic, which consists in placing articles in single series in tandem relation,l enclosing said articles Within a heat exchanging medium but spaced therefrom, providing a heat exchange from the medium to the ends of the pins and shell, closing the spaces between the' pins and shells, and exerting pressure on the ends of the plastic.v

2. The method of curing plastic articles having outer shells, centering pins, and an intervening wall of plastic, which consists in placing articles in single series in tandem relation, enclosing said articles within a heat exchanging medium but spaced therefrom, providing a heat exchange from the medium to the ends of the pins and shells,'closing lthe spaces between the pins and shells, exerting pressure on the ends of the plastic,

and limiting the closing action by a bottoming on the shells.

3. The method of curing a plastic article having an outer shell and a central pin with an intervening Wall of plastic, which consists in enclosing the article within a heat exchanging medium but spaced therefrom, closing the spaces between the ends of the pin and the shell, providing a heat exchange from the medium to the ends of the pin and shell, and exerting pressure on the ends of the article.

4. The method of curing a plastic article having an outer shell anda central pin with an intervening wall of plastic, which consists in enclosing the article within a heat exchanging medium but spaced therefrom, closing the spaces between the ends of the pin and the shell, providing a heat exchange from the medium to the endsof the pin and shell, exerting pressure on the ends of the article, and limiting the vclosing action by 'a bottoming on the shell.

5. The method of curing plastic articles having thin walled outer shells,fcentering-pins, and an intervening wall of plastic, which consists in placing articles in single series in tandem relation,

'enclosing said articles within a heat exchanging -medium but spaced therefrom, providing a heat exchange from the medium to the ends of the pins and shells, closing the spaces between the pins and shells, exerting pressure on the ends of the plastic, limiting the closing action by a bottomving on the shells, and controlling the pressure to -correspond with the pressure capacity of the wall Vacentral pin and a surrounding wall of plastic which consists in placing the articles in a single series in tandem relation, enclosing said articles with the surrounding molds in a heat exchanging medium, but with the molds spaced therefrom, providing a heat exchange from the medium to the ends of the article; exerting pressure on the articles in such tandem relation, and limiting the pressure by a bottoming pressure on the molds.

8. In a plastic curing apparatus, the combination of a mold comprising opposing end closure caps adapted to engage and center an outer shell and a central pin within the shell and with the shell spaced inwardly from the outer edge'of the caps and to transfer heat to the shell and to the pin; a guiding means in heat exchanging relationl with the caps holding the caps in concentric relation; and a pressure device exerting pressure on the caps.

9. In a plastic curing apparatus, the combination of a mold comprising opposing end closure caps having outer sockets spaced inwardly from their edges and adapted to receive and center and bottom on an outer shell and inner sockets within the outer sockets adaptedto receive an inner pin, said caps being adapted to convey heat to the pin and shell; a guiding means in heat exchanging relation with the caps holding the 'caps in concentric relation; and a pressure device exerting pressure on the caps.

10. In a plastic curing apparatus, the combination of a plurality of pairs of end closure caps each pair being adapted to engage and center an outer shell and a central pin within the shell and with the shell spaced inwardly from the outer edge'of the caps and to transfer heat to the shell and to the pin; a guiding means in heat exchanging relation with the caps holding the caps in concentric relation; and a pressure device exerting pressure in tandem on the caps.

l1. In a plastic curing apparatus, the combination of a plurality of pairs of end closure caps,

eachv pair'having outer sockets spaced inwardly from their4 edges and adapted toreceive and center and bottom on an outer shell and inner sockets within the outer sockets adapted to receive an inner pin, said caps being adapted to convey heat to the pin and shell; a guiding means in heat exchanging relation with the caps holding the caps in concentric relation; and a pressure device exerting pressure in tandem on the caps.

' HUGH C. LORD. 

